Low temperature gas decomposition plant



Jan. 26, 1965 A. SELLMAIER 3,167,417

LOW TEMPERATURE GAS DECOMPOSITION PLANT Original Filed Aug. 4, 1959INVENT OR BY v/ vlu/ A2 ATTORNEY5 chambers with diiferent temperatures.

United States Patent M '3 Claims. (a. 62-42) This invention relates toan arrangement for cold insulation in technical large-scale apparatusfor methods of gas liquefaction and/or gas separation to be carried outat low temperatures. The invention uses primarily those temperatureranges which are below the condensation temperature of nitrogen. Atatmospheric pressure this is 77.4 K., hence the invention concernsprimarily insulation arrangements for sheathing parts operating attemperatures below approximately 80 K.

The invention concerns mainly apparatus which contains liquid hydrogenor similar cold liquids, such as liquid helium, neon or mixturesthereof.

On a laboratory scale, the cold insulation heretofore was generallyeffected by arranging the apparatus in a vacuumparticularly a highvacuum. In industrial plants .which exceed laboratory scale it isdifficult to produce a jacket that surrounds the entire plant whichseals vacuumtight on all sides. With dimensions of about 4 to 5 m.height and width respectively the exped-iture for obtaining asatisfactory vacuum and a vacuum-tight jacket respectively presentsconsiderable difficulties. The difficulties increase if a simplecylindrical form of the jacket is abandoned-in order to save materialinfavor of a shape that tapers to the top or bottom.

Known modes for solving this insulation problem consist in surrounding alow-temperature plant working with liquid hydrogen with two differentfitted cylindrical jackets. Such proposals have become knownparticularly for a gas decomposing plant for separating deuterium fromliquid hydrogen. The lower part of the rectifying column arrangementproper together with the other parts working at the above-mentioned lowtemperatures is surrounded by a cylindrical jacket which is sealedmoistureproof on all sides and filled on the inside with gaseoushydrogen. The upper part of the rectifying column arrangement isconducted at the top through the cover of this cylindrical jacket andsurrounded with a second cylinder of a smaller diameter, which secondcylinder is attached on the insulating jacket underneath. The uppercylinder is sealed vacuum-tight and evacuated on the inside. Thisarrangement has the great disadvantage, however, that considerable heatconduction and consequently cold losses appear in the butt joint of thejackets.

The difficulty underlying the problem is that it is not possible to usenitrogen as aninsulating atmosphere at these low temperatures.Insulation with hydrogen alone is not sufficient, however, particularlyfor the colder parts of the rectifying column. For this reason this partof the known plant was also provided with a vacuum jacket.

The object of the invention is to find a different solution for theinsulation problem, where a butt joint between two ditlerent adjacentinsulation jackets is to be avoided under any circumstances.

In order to maintain the temperatures and temperature differencesrequired for the invention, a special elaboration of the idea of theinvention provides for the housing of the different pieces of apparatusin two separate insulated These two insu- 3,167,417. Patented Jan. 26,1965 lated chambers are formed by two insulating casings one inside theother, which together enclose the most importantpreferably allof thepieces of apparatus of the plant which function at temperatures belowthe condensation temperature of nitrogen, and the outer casing enclosesat least a few and preferably all of the remaining pieces of apparatusfunctioning at higher temperatures, although in certain cases these maystill be lower than 273 K., the inner casing being filled with gaseoushydrogen and the outer casing with gaseous nitrogen.

For actual cold insulation, each casing is filled in the conventionalmanner with the usual insulating materials, such as slag wool, glassWool, spun materials from polymerization products, as, for instance,polystyrene, asbestos or similar substances, in some cases at leastpartially in powder form.

Instead of the gases mentioned above-hydrogen and nitrogenother gases ormixtures of gases can also be used, which do not condense at thetemperatures prevailing in the interstices of the insulating material.Thus at least the inner casing may contain, for instance, instead of oras well as hydrogen, helium, neon or a similar gas, or a mixture of anytwo or more of these. Where the inner and the outer casings containdifferent gases, it is an essential condition that the gaseous fillingsof the inner and outer casings do not together form an explosivemixture. Thus for instance, in the absence of hydrogen in the innercasing, air or another gaseous mixture containing oxygen can be used inthe outer casing.

To insure that the gaseous atmosphere in the two casings is maintained,the inner casing, in accordance with a special elaboration of the ideaof the invention, is constructed of a cold resistant material, forexample cold resistant metal, such as aluminum or a suitable steel, suchas V2A steel or a tempered steel, or copper, and is welded wherevernecessary in such a way as to be gas-tight.

The necessary apertures for communication between the two casings aremade with turned and/or ground flanges into which the closing pieces arevery closely fitted. 0n the outer casing the closures are at leastfitted with rubber sealing joints in the conventional manner.

In a further elaboration of the invention, a pressure slightly higherthan that in the outer casing is produced in the inner casing, in orderto prevent the entry of condensable gas in the event of the innerchamber not being quite gas-tight. In order to maintain this excesspressure, the pressure in the inner chamber and in the outer chamher isregulated. As in the inner casing at leastand to a certain degree alsoin the outer casing-there is a vertical temperature gradient, at leastwhen there is a fractionating column in the center, for instance for thepurpose of deuterium extraction, the difierence of pressure between theinner and the outer casing varies at dilierent heights. The excesspressure must therefore be regulated so that at every point in the innerchamber the prevailing pressure is greater than that in the outerchamber. The pressure in the outer chamber may conveniently be keptslightly above atmospheric pressure. In the example described in whichthe inner filling is hydrogen and the outer filling nitrogen, a pressuredilterence of about 50-300 kg./m. (water column) between the inner andouter pressure and about -200 kg./m. (water column) between the outerpressure and atmospheric pressure obtains.

Each casing is equipped in suitable places, for instance at the top andat the bottom, with one inlet or outlet orifice for regulating thepressure. The simultaneous adjustment of inlet and outlet produces acertain direction of flow. This can be chosen as required, so that iteither follows the direction of the pressure drop in the casingconcerned, or runs contrary to it.

The replacement of the quantities of gas necessary to compensate forlosses can be effected either as required or at a fixed rate, in somecases continuously. In the latter case a certain permanent throughstream is main tained.

* In the drawing,.one version of the heat insulation in accordance withthe invention is diagrammatically shown as an example.

In the single figure of drawing, a fractiouating column for separatingdeuterium from liquid hydrogen is shown at 1, the fractionating columnbeing surrounded by two spaced casings 2 and 3, one fitted over theother. Both are cylindrical in their top and bottom parts, with anintermediatc, tapering portion roughly in the middle. In the twoinsulating chambers thus formed, various other auxiliary piece ofapparatus are installed, of which an accessory column 4 in the innerchamber and in the outer chamber the regenerators 5 are indicateddiagrammatically. Each chamber is packed with slag wool. In ti e innerchamber is gaseous hydrogen with a pressure pi; in the outer chamber isgaseous, pure nitrogen with a pressure pa. If p0 designates the pressureof the surrounding air atmosphere, then the condition pi pa po should befulfilled. For the maintenance of the re quired pressure, the entrancesto the insulation chambers are fitted with automatic or hand-operatedpressure reducing valves 6 and 7, whereas overflow valves 8 and 9 arefitted in the outlets. The hydrogen flows in at the top through 6 andflows out at-the bottom through while the nitrogen flows in at thebottom '7 and flows out at the top through 8.

The inner insulation chamber rests on a heat insulating foundation it],which is sealed olf below by a metal plate 11 which is welded into thecasing 2, so that the inner in sulation chamber is completely encased onall sides.

The outer insulation chamber could actually also be constructed in thesame way. However, in the example given it is sufficient for the metalplate 11 to be large enough to cover the base of the outer insulationchamber at the same time, as well the outer casing being attached to itat the bottom by means of a flange. The whole construction stands in theconventional manner on a concrete foundation 12 in which a heatinsulating layer of masonry 13 is inserted in the immediate vicinity ofthe insulation structure in order to reduce the heat gradient.

The outer' casing 3 is constructed in the conventional manner and ismade of copper, VZA steel or a tempered,

cold-resistant steel.

The inner casingg is made of aluminum or also of a tempered,cold-resistant steel, and is composed of several cylindrical elements.The separate elements are assembled on the site and welded together. Thewelded seams must subsequently be subjected to an expansion treatment.

Before being welded together the separate cylindrical elements areassembled and screwed together by means of suitable flanges-14 and 14',15 and 15', etc. Finally the various joints, the vertical ones as wellas the horizontal annular joints, are covered over on the outside withstrips or rings 16, 17, etc., of a material of'particu- 'larly highnotch impact strength at low temperatures, such as above all copper,which may have suitable corrugation in order to enable them to give wayin the face of stresses occurring due to the various coolingtemperatures of the casing 2. The edges of sheet metal strips 16, 17,etc., are welded onto the surrounding parts of the casing. As thecovering strips fixed on are relatively thin in comparison to thethickness of the casing, their assembly is particularly simple and treeof tension.

This application is a division of applicants co-pending applicationSerial No. 831,679, filed August 4, 1959, now Patent No. 3,107,992.

I claim:

1. Means for the thermal insulation of plants consisting of severalapparatus parts operating at different temperatures includingtemperatures below the condensation temperature of nitrogen, whichcomprises at least two spaced insulating casings disposed one over theother, the casings being packed with insulating material, both casingstogether enclosing the apparatus parts operating at the lowesttemperature in the plant, the outer casing alone enclosing otherapparatus parts operating at higher temperatures though still below 0C., the inner casing containing a gaseous medium having a boiling pointat least no higher than that of the gas operating in the apparatus, theouter casing containing a gaseous medium with a poor heat conduction anda higher boiling point than that of the gas being contained in the innercasing.

2. Means for the thermal insulation of plants consisting of severalapparatus parts operating at different temperatures includingtemperatures below the condensation temperature of nitrogen, whichcomprises at least two insulating casings disposed one over the other,the casings being packed with insulating material, both casings togetherenclosing the apparatus parts operating at the lowest temperature in theplant, the outer casing alone enclosing other apparatus parts operatingat higher temperatures though still below 0 C., the inner casingcontaining a gaseous medium with a boiling point at least not higherthan that of the gas operating in the apparatus, the gas contained inthe inner casing and the gas operating in the apparatus not beingexplosive it mixed, the outer casing containing a gaseous medium whichis a poor conductor of the heat and is not explosive when mixed with thegas contained in the inner casing.

3. Means for the cold insulating of plants consisting of severalapparatus parts operating at different temperatures, preferably wheretemperatures are below the condensation temperature of nitrogen, whichcomprises at least two insulating casings disposed one over the other,the casings being packed with insulating material, both casings togetherenclosing the apparatus parts operating at the lowest temperature in theplant, the outer casing alone enclosing other apparatus parts operatingat higher temperatures though still below 0 C., the inner casingcontaining a gaseous medium under ahigher pressure than that of thesurrounding atmosphere and having a boiling point at least no higherthan that of the gas operating in the apparatus, the outer casingcontaining a gaseous medium which is a poor conductor of heat and beingpresent at a pressure between the pressure of the gas contained in theinner casing and the pressure of the surrounding atmosphere.

4. Means for the cold insulating of plants consisting of severalapparatus parts operating at different temperatures, preferably wheretemperatures are below the condensation temperature of nitrogen, whichcomprises at least two insulating casings disposed one over the other,the casings being packed with insulating material, both casings togetherenclosing the apparatus parts operating at the lowest temperature in theplant, the outer casing alone enclosing other apparatus parts operatingat higher emperatures though still below 0 C., the inner casingcontaining the same gas as the gas'operating in the apparatus, the outercasing containing nitrogen in the gaseous state.

5. Means for the cold insulating of plants consisting of severalapparatus parts operating at different temperatures, preferably wheretemperatures are below the condensation temperature of nitrogen, whichcomprises at least two insulating casings disposed one over the other,

'the casings being packed with insulating material, both casingstogether enclosing the apparatus parts operating at the lowesttemperature in the plant, these apparatus parts standing on a heatinsulating base, the base being set on a metal plate which seals theinner casing, the metal plate being underpinned with heat-insulatingmasonry material, the outer casing likewise being sealed by means ofsaid metal plate and alone enclosing other apparatus parts operating athigher temperatures though still below 0 C., the inner casing containinga gaseous medium 2,777,295 Bliss et a1. J an. 15, 1957 having a boilingpoint at least no higher than that of the 2,863,297 Johnston Dec. 9,1958 gas operating in the apparatus, the outer casing contain- 3,057,167Ye dall t a1, Oct 9, 1962 ing a gaseous medium which is a poor conductorof heat, the inner casing having at the highest point therein a 5FOREIGN PATENTS conduit and at the lowest point a valved outlet line to181352 Great Britain 19 1923 regulate the pressure in the inner casing,the outer casing having at the lowest point a conduit and at the highestOTHER REFERENCES point a valved outlet line to regulate the pressure inthe Outer casing 10 Chemical Eng neering Progress (volume 54, Number 6),June 1958, Trrnnierhaus et a1. (page 39 relied on). References cued mthe file of this Patent Some Aspects of Heavy-Water Production byDistilla- UNITED STATES PATENTS tion of Hydrogen (B. M. Bailey),published June 1958,

1,910,024 Le Rouge May 23, 1933 (P 5 and 6 relied

1. MEANS FOR THE THERMAL INSULATION OF PLANTS CONSISTING OF SEVERALAPPARATUS PARTS OPERATING AT DIFFERENT TEMPERATURES INCLUDINGTEMPERATURES BELOW THE CONDENSATION TEMPERATURE OF NITROGEN, WHICHCOMPRISES AT LEAST TWO SPACED INSULATING CASINGS DISPOSED ONE OVER THEOTHER, THE CASINGS BEING PACKED WITH INSULATING MATERIAL, BOTH CASINGSTOGETHER ENCLOSING THE APPARATUS PARTS OPERATING AT THE LOWESTTEMPERATURE IN THE PLANT, THE OUTER CASING ALONE ENCLOSING OTHERAPPARATUS PARTS OPERATING AT HIGHER TEMPERATURES THOUGH STILL BELOW0*C., THE INNER CASING CONTAINING A GASEOUS MEDIUM HAVING A BOILINGPOINT AT LEAST NO HIGHER THAN THAT OF THE GAS OPERATING IN THEAPPARATUS, THE OUTER CASING CONTAINING A GASEOUS MEDIUM WITH A POOR HEATCONDUCTION AND A HIGHER BOILING POINT THAN THAT OF THE GAS BEINGCONTAINED IN THE INNER CASING.